The need for maintaining clear visibility through viewing windows has long been recognized, particularly in the automobile industry, the shipping industry, the tooling and machining industry, and in many other areas where clear visibility through a window is required.
Visibility through a viewing window is commonly impeded when, for example, water and other debris impacts the window. In the automotive and shipping industry, reciprocating wipers have been used to remove water and debris from windshields. Windshield wipers cannot, however, overcome the problem of water collecting on the windshield in between swipes of the wiper, regardless of the speed at which the wiper reciprocates.
In the machining and tooling industry, there is a need to maintain the window through which the work piece is viewed clear of coolant used in machining and scraps of metal and debris resulting from the machining process. Wire screens have been used to protect the window from flying pieces of debris. However, use of a screen tends to impede, rather than improve, visibility through the window.
In all of the above-mentioned applications, a need exists not only to maintain the viewing window free of water and other debris, but also to keep intact as much of the structural integrity of the viewing window as possible. Preferably, there should be no reduction in such structural integrity for safety reasons.
Rotating windows have been used to overcome some of the above-noted problems in the shipping and machining industry. A rotating window places a centrifugal force on any object that comes into contact with the window and slings the object immediately off the rotating window.
Prior known rotating windows suffer, however, from several drawbacks. First, traditional mounting techniques for windows have required that some type of a mounting hole be cut through the viewing window. This, of course, weakens the strength of the viewing window and creates safety concerns. Further, the bigger the rotating window, the bigger the hole must be and the weaker the viewing window becomes. Stress cracks commonly originate from the edges of such a mounting hole which further weaken the strength of the window.
Another problem with respect to known prior rotating windows is that they must typically be installed on an existing enclosure that has a stationary or viewing window. Such installation requires cutting a hole in the viewing window and mechanically securing the rotating window to the stationary window, which is labor intensive and therefore expensive. Further, holes cannot generally be cut into windows made of certain materials, such as glass that has already been tempered, and laminated safety glass.
Another problem associated with prior rotating windows is that they have a tendency to fog up. These prior rotating windows have one sheet of transparent material facing the area to be viewed that rotates and a second sheet of transparent material closest to the person looking through the rotating window. This second sheet is stationary and overlies the opening which has been cut in the larger viewing window. If moisture, such as from water or lubricants, enters into the area in between the two sheets of material, the transparent materials will fog up. The problem of moisture entering in between the sheets of material commonly arises when the rotating window has been deactuated.
A further problem created by prior rotating windows is that because they are mounted through holes, they create a tunnel-vision effect, from the length of cylindrical window housing, that restricts the angle of vision of the operator through the rotating window.